Polish, e2e tests, better first user experience

[SmilyOrg]

• Logs: timestamp is not shown anymore as I didn't find it useful (logging systems usually provide their own). Let me know if it was useful to you. All exposed urls are now shown on startup, so it's more obvious how to access it.

  app running (api under /api)
    local    http://127.0.0.1:8080
    network  http://172.22.0.27:8080
  

• Loading & errors: there are more loading indicators, especially for loading collections, so that it doesn't just show a white screen. If the connection to the server drops, there is also a more obvious error message and status shown. Same if you run it without any collections configured. Fixes Better loading indicators #84.
  
  

• Autoreload: the configuration should be automatically reloaded on yaml file change, so restarting is not required anymore. The same applies to collections with expand_subdirs: true, if you change the dirs the server is automatically reloaded.

• Rescan applies faster: previously the view was sometimes cached "too much" leading to it showing the same thing, even after a rescan and page reload. Switching back to the photos or refreshing the page should now always show the up to date view, resolving point 1 in Refreshing the view can be way more complicated than it should be #81 from the scanning point of view.

• Cleaner exit: if you Ctrl+C or otherwise "soft close" (SIGTERM) the app, it should close the database cleanly, so -shm and -wal files are not left laying around anymore. They are still left if you forcibly close the app (SIGKILL) as that cannot be handled.

• Layout fixes: timeline view shouldn't overlap with the app bar on top anymore. Small collections should now be top-left aligned and not centered. The "Wall" layout was bugged and should now work as expected again.

• Add Playwright e2e tests: this should make it easier to make sure that some of the features above keep working as expected in the future. Still a bit of a proof of concept though.

• File reorganization: the UI, docs, and e2e tests are now there as three independent nodejs projects so that you don't have to install all of them to work on just one.